Duplex communication method, base station and terminal

ABSTRACT

The present disclosure relates to a pre-5th-Generation (5G) or 5G communication system to be provided for supporting higher data rates beyond 4th-Generation (4G) communication system such as Long Term Evolution (LTE). A bidirectional communication method and an apparatuses thereof are provided. An uplink control channel and a downlink control channel are respectively transmitted in a first subband and a third subband of an available un-paired spectrum, wherein control channels of reverse directions are transmitted at the same time in the first subband and the third subband, and uplink data and downlink data are transmitted in a time division multiplexing manner in a second subband of the available un-paired spectrum, wherein the first subband and the third subband are on the two ends of the available un-paired spectrum.

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM OF PRIORITY

The present application is a continuation of U.S. application Ser. No.15/349,999, filed Nov. 11, 2016, which is related to and claims priorityunder 35 U.S.C. § 119(a) of a Chinese patent application filed in theChinese Intellectual Property Office on Nov. 13, 2015 and assignedSerial No. 201510779297.0, the entire disclosures of which areincorporated herein by reference.

BACKGROUND 1. Field

The present disclosure relates to wireless communication techniques, andmore particularly, to a duplex communication method, a base station anda terminal.

2. Description of Related Art

To meet the demand for wireless data traffic having increased sincedeployment of 4G (4th-Generation) communication systems, efforts havebeen made to develop an improved 5G (5th-Generation) or pre-5Gcommunication system. Therefore, the 5G or pre-5G communication systemis also called a ‘beyond 4G network’ or a ‘post LTE system’.

The 5G communication system is considered to be implemented in higherfrequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higherdata rates. To decrease propagation loss of the radio waves and increasethe transmission distance, the beamforming, massive multiple-inputmultiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna,an analog beam forming, large scale antenna techniques are discussed in5G communication systems.

In addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud radioaccess networks (RANs), ultra-dense networks, device-to-device (D2D)communication, wireless backhaul, moving network, cooperativecommunication, coordinated multi-points (CoMP), reception-endinterference cancellation and the like.

In the 5G system, hybrid FSK and QAM modulation (FQAM) and slidingwindow superposition coding (SWSC) as an advanced coding modulation(ACM), and filter bank multi carrier (FBMC), non-orthogonal multipleaccess (NOMA), and sparse code multiple access (SCMA) as an advancedaccess technology have been developed.

With rapid development of information industry, especially increasingrequirements from mobile Internet and Internet of things (IoT), mobilecommunication techniques are facing unprecedented challenges. Accordingto International Telecommunication Union (ITU) report ITU-RM.[MT.BEYOND2020.TRAFFIC], it can be predicted that as of 2020, mobileservice amount will increase 1000 times compared with 2010 (4G era), andthe connected user devices will exceed 17 billion. With involvement ofIoT devices into the mobile communication networks, the number ofconnected user devices may be more astonishing. Under the unprecedentedchallenges, communication industry and the academia have startedintensive researches in fifth generation mobile communication techniques(5G) facing 2020. At present, architecture and global objective offuture 5G have been discussed in the ITU report ITU-R M.[IMT.VISION],which provides detailed description to requirement prospect, applicationscenarios and various important performances of 5G. With respect to newrequirement of 5G, the ITU report ITU-R M.[MT.FUTURE TECHNOLOGY TRENDS]provides information related to technology trends of 5G, aims to solvedramatic problems such as system throughput, user experienceconsistency, extendibility, supporting IoT, tendency, efficient, cost,network flexibility, supporting of new services and flexible spectrumutilization.

Duplex mode in wireless communications refers to a processing manner ofuplink and downlink bidirectional data communications and forms animportant basis for air-interface design of the wireless communications,which is no exception in the research of 5G. At present, FrequencyDivision Duplex (FDD) and Time Division Duplex (TDD) are two main duplexmodes and have been widely used in broadcast audio and video fields andcivil communication systems, e.g., Long Term Evolution (LTE) systemcorresponding to the Evolved Universal Terrestrial Radio Access (E-UTRA)protocol defined by 3rd Generation Partnership Project (3GPP), IEEE802.11a/g Wireless Local Area (WLAN), etc.

In the FDD mode, uplink and downlink communications use paired frequencyresources having a certain duplex spacing. However, in the TDD mode,uplink and downlink share the same frequency resources, and uplinkcommunication and downlink communication are implemented via differenttime resources. Different duplex modes result in different physicallayer designs for air interface such as frame structure. Take LTE as anexample, two kinds of frame structures are defined in LTE respectivelyapplicable for the FDD mode and the TDD mode.

The FDD frame structure is as shown in FIG. 1. Each radio frame is of 10ms length, consists of ten 1 ms subframes. Each subframe consists of two0.5 ms slots. Uplink communication and downlink communication areimplemented using different frequency resources.

The TDD frame structure is as shown in FIG. 2. Similar as the FDD framestructure, each radio frame is of 10 ms length, consists of ten 1 mssubframes. The difference relies in that, the uplink communication anddownlink communication in the TDD mode share the same frequencyresources and are differentiated through time resources. For example, inthe configuration as shown in FIG. 2, subframes 0, 5 are used fordownlink communication, and subframes 2, 3, 4, 7, 8 and 9 are used foruplink communication. In order to ensure that the downlink communicationdoes not affect the uplink communication, a special subframe isintroduced in the TDD frame structure, i.e., the subframes 1 and 6 asshown in FIG. 2. The special subframe consists of a Downlink Pilot TimeSlot (DwPTS), a Guard Period (GP) and an Uplink Pilot Time Slot (UpPTS).In the TDD frame structure, subframes 1, 5 and the DwPTS are always usedfor downlink transmission, whereas UpPTS and its subsequent subframesare always used for uplink transmission. The GP is a guard periodbetween the downlink communication and the uplink communication, so asto ensure that the uplink data communication is not affected by thedownlink communication. The LTE TDD mode may be configured flexibly, soas to support uplink/downlink asymmetric services. Table 1 shows variousconfigurations of the LTE TDD mode, wherein D denotes that the subframeis used for downlink communication, U denotes that the subframe is usedfor uplink communication, and S denotes the special subframe.

TABLE 1 uplink-downlink configurations of LTE TDD mode Downlink- Uplink-uplink downlink switching Subframe index configuration periodicity 0 1 23 4 5 6 7 8 9 0 5 ms D S U U U D S U U U 1 5 ms D S U U D D S U U D 2 5ms D S U D D D S U D D 3 10 ms  D S U U U D D D D D 4 10 ms  D S U U D DD D D D 5 10 ms  D S U D D D D D D D 6 5 ms D S U U U D S U U D

The above two duplex modes each have their advantages and disadvantages.In particular, the FDD mode requires paired frequency bands to implementuplink and downlink data communications, and the paired uplink anddownlink frequency bands need a certain duplex spacing. In the case that5G is developed towards high frequency and wide bandwidth, it may resultin spectrum fragments from the perspective of spectrum division and thusis not good for spectrum management. The TDD mode uses the same spectrumfor the uplink and downlink data communications. Therefore, the TDD modehas advantages in terms of spectrum utilization flexibility. It cansupport more asymmetric services and have higher spectrum utilizationratio. As to the FDD, since the spectrum is paired, the uplink anddownlink resources are always available. Thus, the scheduling and theuplink control signaling fed back by the terminal are relatively intime, e.g., Acknowledge/Negative-Acknowledge (ACK/NACK) of HybridAutomatic Retransmission reQuest (HARQ) and Channel State Information(CSI). As such, feedback delay of the air interface may be reduced, andthe scheduling efficiency is increased. However, as to the TDD, thedifferent uplink-downlink configurations lead to complex design. Inaddition, the TDD mode has the advantages of uplink/downlink channelreciprocity, which may greatly simplify the obtaining of the CSI.

Large-scale MIMO technique may be adopted in 5G to further increase thespectrum efficiency. The base station is equipped with a large amount ofantennas. Thus, in the FDD mode, a large amount of resources may berequired for downlink physical channel training and feedback of channelstate information. However, the overhead of training and feedback may begreatly decreased utilizing the channel reciprocity under the TDD mode.Therefore, the TDD mode is more attractive for the large-scale MIMOtechnique. But 5G also has the requirement of low latency, and needs tofurther shorten the air interface transmission time interval (TTI) andcontrol signaling, which makes the design of the TDD mode more complex.

It can be seen from the above analysis that, the FDD mode and the TDDmode respectively have their advantages and disadvantages. Facing theapplications of rich application scenarios and new frequency band in 5G,it is necessary to design a new duplex mode, to combine the advantagesof the FDD mode and the TDD mode, so as to ensure 5G spectrumutilization ratio and network performance better.

SUMMARY

The technical problem to be solved by the present disclosure is that,the FDD mode and the TDD mode in the wireless communication systemoperate independently and cannot be combined, which restricts thespectrum utilization ratio and the performance of the wirelesscommunication system. To address the above-discussed deficiencies, it isa primary object to provide an in-band duplex communication method, abase station and a terminal.

A bidirectional communication method provided by the present disclosureincludes: transmitting an uplink control channel and a downlink controlchannel respectively in a first subband and a third subband of anavailable un-paired spectrum, wherein control channels of reversedirections are transmitted at the same time in the first subband andthird subband; and transmitting uplink data and downlink data of a datachannel in a time division multiplexing manner in a second subband ofthe available un-paired spectrum, wherein the first subband and thethird subband are on the two ends of the available un-paired spectrum.

In one embodiment, there is a guard band between the first subband andthe second subband, there is another guard band between the secondsubband and the third subband, and no signal is transmitted in the guardbands.

In one embodiment, the size of the guard bands is determined accordingto an interference level of adjacent subbands and an out-of-band leakagesuppression technique being used.

In one embodiment, the method further includes: adjusting, by a basestation, the size of the guard bands through at least one of thefollowing guard band modes:

inserting an additional guard band in at least one of the subbands; and

adjusting a center frequency point of the data channel in at least onesubframe of the second subband.

In one embodiment, the method further includes: adjusting the guard bandmode dynamically according to uplink received signal strength, andindicating the currently utilized guard band mode to a terminal througha predefined manner or a broadcast channel or the downlink controlchannel.

In one embodiment, the method further includes: storing a relationshipbetween the guard band mode and an index of the guard band mode in alooking-up table, and signaling the currently utilized guard band modeto the terminal through indicating the index of the currently utilizedguard band mode within the looking-up table.

In one embodiment, in the guard band mode in which the additional guardband is inserted in at least one subband, parameters being adjustedcomprise: position and size of the additional guard band inserted in thecontrol channel and/or the data channel; and

in the guard band mode in which the center frequency point of the datachannel is adjusted, parameters being adjusted comprise: an offset ofthe center frequency point of the data channel.

In one embodiment, the method further includes: notifying, by the basestation, the terminal of a position and a bandwidth of each subbandwithin the available un-paired spectrum, and an uplink-downlinkconfiguration of the data channel, and communicating with the terminalaccording to an appointed transmission configuration.

In one embodiment, the downlink control channel is used for transmittingdownlink control signaling, wherein the downlink control signalingcomprises at least one of resource allocation information, modulationand coding scheme information, hybrid automatic retransmission requestacknowledgement/negative-acknowledgement information, an uplinktransmission grant, an uplink transmission power control indication, theuplink control channel is used for transmitting uplink controlsignaling, wherein the uplink control signaling comprises at least oneof a scheduling request, hybrid automatic retransmission requestacknowledgement/negative-acknowledgement information, channel stateinformation, and the second subband is used for transmitting the uplinkdata and the downlink data, and is further used for transmitting atleast one of: a synchronization channel, a broadcast channel fortransmitting system information, and an uplink random access channel.

In one embodiment, a first subframe of each radio frame is used fordownlink transmission.

In one embodiment, the method further includes transmitting, by the basestation, an uplink switch indication and/or a downlink switch indicationin the downlink control channel, to change a transmission direction ofsubframes in the data channel.

In one embodiment, the method further includes transmitting at least oneuplink switch indication in the downlink control channel of each radioframe, and at least one subframe in the data channel is used for uplinkdata communication.

In one embodiment, the method further includes inserting a guardinterval at a downlink-to-uplink switching point, wherein no signal istransmitted during the guard interval.

In one embodiment, the method further includes: inserting a specialsubframe at the downlink-to-uplink switching point, the special subframecomprises: a downlink special slot, a guard period and an uplink pilotslot, wherein the downlink special slot is used for downlinkcommunication, and contents transmitted by the downlink special slotcomprise at least one of: a downlink data channel, a physicalsynchronization channel and a physical broadcast channel, the uplinkpilot slot is used for conveying sounding pilot signal, and no signal istransmitted during the guard period.

In one embodiment, filtered or filter-bank single carrier modulation, orfiltered or filter-bank multicarrier modulation is adopted for eachsubband, wherein the filtered or filter-bank single carrier ormulticarrier modulation comprises any one of: Filter-Bank Multicarrier(FBMC), filtered-OFDM, and Single-Carrier Filter-Bank Multicarrier(SC-FBMC).

In one embodiment, the method further includes adjusting a frequencylocalization of the filter or the filter-bank to match the size of theguard bands.

In one embodiment, the method further includes dividing the secondsubband into at least two subbands, for different subbands, adoptingdifferent filtered or filter-bank single carrier or filtered orfilter-bank multicarrier modulation physical layer parameters.

In one embodiment, the transmitting the uplink control channel and thedownlink control channel respectively in the first subband and the thirdsubband of the available un-paired spectrum comprises transmitting thedownlink control channel and the uplink control channel in the firstsubband alternatively, and at the same time, transmitting in the thirdsubband the control channel of a direction different from thattransmitted in the first subband.

In one embodiment, a guard interval exists between transmissions of thedownlink control channel and the uplink control channel in the samesubband, and no signal is transmitted during the guard interval.

In one embodiment, alternating frequencies of the alternativetransmission of control channels in the first subband and the thirdsubband are the same, and are provided to the terminal via a predefinedmethod or through the downlink control channel or through the broadcastchannel in the first subframe.

In one embodiment, the method further includes transmitting, by the basestation, control signaling in the data channel of the second subband,and informing the terminal whether control signaling is transmitted inthe data channel of the second subband through the downlink controlchannel in the first subband or the broadcast channel in the secondsubband, wherein the base station transmits the control signaling in thedata channel of the second subband via at least one of the following:transmitting signaling of the downlink control channel using partialtime-frequency resources of downlink subframes in the data channel,transmitting signaling of the uplink control channel using partialtime-frequency resources of uplink subframes in the data channel.

Embodiments of the present disclosure further provide a base stationincluding a control signal transmitting module (transmitter) and a datasignal transmitting module (transmitter). The control transmittingmodule is adapted to transmit an uplink control channel and a downlinkcontrol channel respectively in a first subband and a third subband ofan available un-paired spectrum, and control channels of reversedirections are transmitted in the first subband and the third subband atthe same time, the data transmitting module is adapted to transmituplink data and downlink data of a data channel in a time divisionmultiplexing manner in a second subband of the available un-pairedspectrum. The first subband and the third subband are located at the twoends of the available un-paired spectrum.

Embodiments of the present disclosure further provide a terminalaccessing method, includes implementing, by a terminal, a cell searchingprocedure through receiving a synchronization channel and a broadcastchannel in a center position of a second subband, and obtaining systemconfiguration information through reading the broadcast channel, whereina time-frequency position of the synchronization channel and atime-frequency position of the broadcast channel are preconfigured in aframe structure, and the system configuration information comprises atleast one of: system bandwidth, uplink-downlink configuration, guardband configuration, and control channel frequency hopping configuration,obtaining, by the terminal through the system configuration informationin the broadcast channel, a center frequency point position and abandwidth of an uplink control channel and a downlink control channel, acenter frequency point and a bandwidth of a data channel, and anuplink-downlink configuration, obtaining, by the terminal through thedownlink control channel, other system configuration information born bydownlink subframes of a data channel, and initiating and finishing anuplink access according to the other system configuration information,communicating, by the terminal, with the base station according to anappointed uplink-downlink configuration.

In one embodiment, based on predefined looking-up table, the terminalobtains the uplink-downlink configuration, the guard band configurationand the control channel frequency hopping configuration throughreceiving an index from the base station respectively.

In one embodiment, the terminal determines a Hybrid AutomaticRetransmission request Acknowledgement/Negative Acknowledgement (HARQACK/NACK) position according to position of subframes used for uplinkand downlink data communications in the data channel.

In one embodiment, the terminal determines uplink and downlink HARQACK/NACK positions according to a fixed HARQ Round Time Interval (RTT).

Embodiments of the present disclosure further provide a terminal,including: a cell searching module, a configuration informationobtaining module, an access module and a communication module, whereinthe cell searching module is adapted to implement a cell searchingprocedure through receiving a synchronization channel and a broadcastchannel on a center frequency position of a second subband, andobtaining system configuration information through reading the broadcastchannel. The time-frequency position of the synchronization channel andthe time-frequency position of the broadcast channel are preconfiguredin a frame structure, the system configuration information comprises atleast one of: system bandwidth, uplink-downlink configuration, guardband configuration, and control channel frequency hopping configuration,the configuration information obtaining module is adapted to obtaincenter frequency points and bandwidths of an uplink control channel anda downlink control channel, a center frequency point and a bandwidth ofa data channel, and uplink-downlink configuration according to thesystem configuration information in the broadcast channel, the accessmodule is adapted to obtain other system configuration information bornby downlink subframes of a data channel via the downlink controlchannel, and initiate and finish an uplink access according to the othersystem configuration information, and the communication module(transceiver) is adapted to communicate with the base station accordingto an appointed uplink-downlink configuration.

In the bidirectional communication method and device provided byembodiments of the present disclosure, the uplink control channel andthe downlink control channel are respectively transmitted in the firstsubband and the third subband of the available un-paired spectrum,wherein control channels of reverse directions are transmitted in thefirst subband and the third subband at the same time; and uplink dataand downlink data are transmitted in a time division multiplexing modein the second subband of the available un-paired spectrum. It is notrequired to allocate multiple bands. The un-paired spectrum may bedirectly divided into subbands. Interferences between the subbands arerestrained utilizing out-of-band leakage suppressing technique and theguard bands. The spectrum utilization ratio and performance of thewireless communication system are improved.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document: the terms “include” and “comprise,” aswell as derivatives thereof, mean inclusion without limitation; the term“or,” is inclusive, meaning and/or; the phrases “associated with” and“associated therewith,” as well as derivatives thereof, may mean toinclude, be included within, interconnect with, contain, be containedwithin, connect to or with, couple to or with, be communicable with,cooperate with, interleave, juxtapose, be proximate to, be bound to orwith, have, have a property of, or the like; and the term “controller”or “processor” means any device, system or part thereof that controls atleast one operation, such a device may be implemented in hardware,firmware or software, or some combination of at least two of the same.It should be noted that the functionality associated with any particularcontroller may be centralized or distributed, whether locally orremotely. Definitions for certain words and phrases are providedthroughout this patent document, those of ordinary skill in the artshould understand that in many, if not most instances, such definitionsapply to prior, as well as future uses of such defined words andphrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1 is a schematic diagram illustrating an LTE FDD frame structureaccording to the prior art.

FIG. 2 is a schematic diagram illustrating an LTE TDD frame structureaccording to the prior art.

FIG. 3 is a schematic diagram illustrating an in-band hybrid duplex modeaccording to some embodiments of the present disclosure.

FIG. 4 is a schematic diagram illustrating comparison of waveforms ofFBMC subcarriers and OFDM subcarriers according to some embodiments ofthe present disclosure.

FIG. 5 is a schematic diagram illustrating comparison of spectrums ofF-OFDM and OFDM according to some embodiments of the present disclosure.

FIG. 6 is a schematic diagram illustrating a frame structure accordingto some embodiments of the present disclosure.

FIG. 7 is a schematic diagram illustrating a duplex frequency banddivision according to some embodiments of the present disclosure.

FIG. 8 is a schematic diagram illustrating a data communicationstructure according to some embodiments of the present disclosure.

FIG. 9 is a schematic diagram illustrating flexible uplink-downlinkconfigurations according to some embodiments of the present disclosure.

FIG. 10 is a schematic diagram illustrating an in-band hybrid duplexmode in which guard bands are inserted in the data channel according tosome embodiments of the present disclosure.

FIG. 11 is a schematic diagram illustrating an in-band hybrid duplexmode in which the guard bands are inserted in the control channelsaccording to some embodiments of the present disclosure.

FIG. 12 is a schematic diagram illustrating an in-band hybrid duplexmode in which data channel center frequency point is adjusted accordingto some embodiments of the present disclosure.

FIG. 13 is a schematic diagram illustrating a frequency hoppingtransmission manner of the control channel according to some embodimentsof the present disclosure.

FIG. 14 is a schematic diagram illustrating transmission of controlsignaling in the data channel according to some embodiments of thepresent disclosure.

FIG. 15 is a schematic diagram illustrating a downlink HARQ timingsequence according to some embodiments of the present disclosure.

FIG. 16 is a schematic diagram illustrating an uplink HARQ timingsequence according to some embodiments of the present disclosure.

FIG. 17 is a schematic diagram illustrating structures of asynchronization channel and a broadcast channel according to someembodiments of the present disclosure.

FIG. 18 is a schematic diagram illustrating a structure of a basestation according to some embodiments of the present disclosure.

FIG. 19 is a schematic diagram illustrating a structure of a terminaldevice according to some embodiments of the present disclosure.

DETAILED DESCRIPTION

FIGS. 1 through 19, discussed below, and the various embodiments used todescribe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably arranged telecommunication devices.

The present disclosure will be described in further detail hereinafterwith reference to accompanying drawings and embodiments to make theobjective, technical solution and merits therein clearer.

The present disclosure provides an in-band bidirectional communicationmethod with separated control and data, shortened as In-band HybridDuplex hereinafter. “In-band” means that the present disclosure does notrequire multiple bands. An un-paired spectrum can be directly dividedinto subbands. Interferences between different subbands can be reducedby out-of-band leakage suppressing technique (such as filtered waveformmodulation technique) and guard bands. FIG. 3 is a schematic diagramshowing the in-band hybrid duplex solution provided by some embodimentsof the present disclosure.

In FIG. 3, the time-frequency resources used for data transmission aredivided into three parts in the frequency domain. The two subbands onthe two ends are respectively used for transmitting an uplink controlchannel and a downlink control channel. The subband in the middle isused for transmitting a data channel (also referred to as a “datasubband” hereinafter). In order to avoid interferences between thecontrol channels and the data channel, guard bands are inserted betweenthe subbands. The control channels and the data channel are transmittedusing a manner similar as FDD. But the data channel is transmitted usinga manner similar as TDD, i.e., uplink data and downlink data share thesame frequency band and are differentiated by time. A guard interval isinserted at the downlink-to-uplink switching point, acting as aswitching guard period from the downlink to the uplink, so as to avoidinterferences to uplink receiving caused by the time multiplexingdownlink transmission.

In order to reduce spectrum utilization ratio loss due to the guardbands, the present disclosure adopts “filtered or filter-bank singlecarrier” or “filtered or filter-band multicarrier modulation”, includingbut is not limited to Filter-Bank Multicarrier (FBMC) technique(reference document: “Analysis and design of OFDM/OQAM systems based onfilter bank theory”, IEEE Transactions on Signal Processing, Vol. 50,No. 5, 2002), Filtered-OFDM (F-OFDM) technique (reference document “Theeffect of filtering on the performance of OFDM systems,” IEEE Trans.Veh. Tech., vol. 49, no. 5, pp. 1877-1884, 2000.), Single-CarrierFilter-Bank Multicarrier (SC-FBMC) technique, etc. A common objective ofthese techniques is to filter signals based on filters, so as torestrain out-of-bank leakage, i.e., reducing the interferences betweenthe subbands. Thus, the size of the guard bands can be adjustedaccording to implementations of the filters. The filtered or filter-banksingle carrier or filtered or filter-bank multicarrier modulationincludes filtered single carrier modulation, filtered multicarriermodulation, filter-bank single carrier modulation and filter-bankmulticarrier modulation.

FBMC can achieve waveform with proper time/frequency localization byadopting well-designed prototype filter function, e.g., based onprototype filter functions such as Isotropic Orthogonal TransformAlgorithm (IOTA), or Extended Gaussian Function, or European PHYDYAS.FBMC performs pulse shaping to signals of each subcarrier utilizingfilters with better time/frequency localization, such that: FBMC is ableto restrain ISI caused by multipath without the need of CP, which bringshigher spectrum efficiency and energy efficiency compared to OFDM, andhas a better receiving robustness under larger time error at the sametime, therefore a non-rigid synchronized transmission is allowed;benefit from better frequency localization, FBMC is able to transmitsignals within extremely narrow frequency resources and remain very lowout-of-band leakage. Such that, Inter-Carrier Interferences (ICI)brought out by Doppler or phase noise can be restrained better.Therefore, FBMC requires a narrow guard band for implementing thein-band hybrid duplex, and the saved cyclic prefix offload cancompensate for the offload of the guard bands to some extent. Therefore,the in-band hybrid duplex mode as shown in FIG. 3 is competitive in 5Gfrom the view of spectrum utilization ratio.

FIG. 4 is a schematic diagram showing subcarrier frequency-domainwaveform of FBMC with PHYDYAS filter and that of the OFDM technique withrectangle window function. It can be seen that, compared with the OFDMtechnique, FMBC has better frequency localization, fast frequency-domainwaveform fading and little out-of-band leakage. Therefore, FBMC is verysuitable for the in-band hybrid duplex mode as shown in FIG. 3. It caneffectively reduce adjacent channel interferences, while effectivelyreducing the bandwidth occupied by the guard bands and decreasing theoffload caused by the guard bands.

FIG. 5 is a schematic diagram showing comparison of spectrums of F-OFDMand OFDM with 64 valid subcarriers. The filter adopted by the F-OFDMtechnique is obtained by multiplying a sinc function and a hanningwindow. It can be seen that, compared with the OFDM technique, theout-of-band spectrum fading of the F-OFDM technique is apparentlyfaster. The out-of-band leakage behind several subcarriers out of theband is decreased to a relatively low level. Therefore it can reduce thespectrum efficiency loss caused by the guard bands. A well-designedfilter can let the F-OFDM have a faster out-of-band fading, but atradeoff has to be made between the complexity and signal distortionindex.

The in-band hybrid duplex mode as shown in FIG. 3 has the followingtechnical advantages:

1. Paired spectrums are not required and resource scheduling anduplink-downlink communication configuration are more flexible. Thus,large un-paired bandwidth can be allocated in the new band of 5G, andspectrum fragments are avoided.

2. The uplink and downlink control channels are transmitted over thewhole band. Therefore, the HARQ timing sequence similar to the FDD modecan be adopted, which avoids HARQ timing sequence confusion and the lowefficiency of the TDD mode.

3. Through enhancement of Sounding Reference Signal (SRS) in the datasubband, downlink channel estimation can be implemented through channelreciprocity based on the channel estimation of the uplink channel. Thischaracteristic effectively reduces the offload for channel training andfeedback in large-scale MIMO system, and is very suitable for the highband communication and large-scale MIMO technique in 5G wirelesscommunications.

In order to support the in-band hybrid duplex mode, the terminal has tohave the capability for simultaneously processing signals of differentsubbands. Considering that current mobile communication equipmentgenerally supports both the FDD mode and the TDD mode, they have thecapability for processing signals of different subbands and thereforeare able to support the in-band hybrid duplex mode provided by thepresent disclosure. In addition, when the in-band hybrid duplex mode isadopted, based on the FBMC modulation, asynchronous transmission andlicense exempt small packet data transmission are still able to beimplemented in the data subband in the TDD mode.

Hereinafter, the technical solution of the present disclosure isdescribed in further detail with reference to some embodiments.

Embodiment 1

In this embodiment, a communication system based on the in-band hybridduplex mode is described with reference to detailed system parameterconfigurations. In this embodiment, suppose that the applicationscenario is a high frequency communication scenario in 5G, e.g. acommunication system operating on millimeter band. In order to increasesystem spectrum utilization ratio and reduce out-of-band leakage, a newwaveform multicarrier modulation scheme such as FBMC or F-OFDM which haslittle out-of-band leakage and fast out-of-band fading is adopted.Suppose that the system operates on 28 GHz, the system bandwidth is 150MHz, and subcarrier interval is 300 kHz. At this time, the duration ofone multicarrier symbol is 3.33 us, the multicarrier modulation uses a512-point Fast Fourier Transform (FFT). The radio frame structurefollows that in the LTE, i.e., a radio frame consists of subframes and asubframe consists of slots. In this embodiment, one slot consists of 15multicarrier modulation symbols of 0.05 ms length. One subframe consistsof two slots of 0.1 ms length. One radio frame consists of ten 1 mssubframes. The frame structure described in this embodiment is shown inFIG. 6. The symbols in FIG. 6 refer to multicarrier modulation symbols.It should be noted that, this embodiment adopts the new waveformmodulation technique FBMC, which is able to restrain Inter-SymbolInterference (ISI) caused by multipath channel without adding CyclicPrefix (CP).

FIG. 7 is a schematic diagram illustrating a spectrum structure providedby some embodiments of the present disclosure. One subcarrier in onemulticarrier symbol is defined as a Resource Element (RE). One resourceblock includes 20 subcarriers of 15 multicarrier symbols, i.e., 300 REs,representing a bandwidth of 5 MHz and a length of 0.05 ms. The spectrumstructure as shown in FIG. 7 occupies 150 MHz bandwidth and includes 500available subcarriers.

As shown in FIG. 7, the available bandwidth can be divided into fourparts according to their functions, including an uplink control channel,a downlink control channel, a data channel and guard bands. The 15subcarriers on the two ends of the bandwidth are respectively used fortransmitting the uplink control channel and the downlink controlchannel. The 460 subcarriers in the middle of the bandwidth are used fordata transmission. The 5 subcarriers between the control channel and thedata channel are reserved as the guard band, so as to reduce theinterference between the control channel and the data channel. It isknown from FIG. 4 that the out-of-band leakage behind the 5 subcarrierscan roll off to below 100 dB.

Considering that the new waveform modulation scheme is adopted, theout-of-band leakage is greatly decreased compared to the OFDM technique.Therefore, a relatively narrower bandwidth is required to be reserved asthe guard band to effectively reduce or even eliminate the interferencebetween the data channel and the control channel. The size of the guardband is relevant to the out-of-band suppression capability of the newwaveform modulation scheme, i.e., the frequency localization of thefilter can be adjusted to match the size of the guard band. In thisembodiment, 5 subcarriers are respectively reserved between the datachannel and the downlink control channel and between the data channeland the uplink control channel as the guard bands. Each guard bandoccupies 1.5 MHz bandwidth. For the new waveform modulation techniquessuch as FBMC with low out-of-band leakage, it is enough to eliminate theinter-channel interference caused by the out-of-band leakage. The two1.5 MHz guard bands occupy merely 2% of the whole bandwidth. Comparedwith the 10% guard band reservation in the current LTE OFDM system fortreating spectrum leakage and the exceeding 6% CP overhead, the overheadof the guard bands can be almost ignored.

Functions of each channel as shown in FIG. 7 are as follows.

The downlink control channel is used for transmitting downlink controlsignaling, including resource allocation information, Modulation andCoding Scheme (MCS) of each code word, HARQ information, number oflayers information in case of multi-layer transmission, power controlsignaling of the uplink control channel, trigger of non-periodic SRStransmission, etc. At the same time, the downlink control channel isalso used for transmitting HARQ indication information. That is to say,the downlink control channel includes at least a PDCCH and a PHICHsimilar as the LTE.

The uplink control channel is used for transmitting uplink controlsignaling, including: Scheduling Request (SR), HARQ ACK/NACKinformation, Channel State Information (CSI), etc. The CSI includesChannel Quality Indicator (CQI), and Rank Indicator (RI) and PrecodingMatrix Indicator (PMI) used for MIMO transmission feedback. That is tosay, the uplink control channel includes at least a PUCCH similar as theLTE.

The data channel is used for transmitting uplink and downlink data, andalso a synchronization channel, a broadcast channel used fortransmitting system information and an uplink random access channel. Inother words, it includes at least a PUSCH, a PDSCH, a PRACH, a PBCH andan SCH similar as the LTE. Since the data channel is used for datacommunications of both the uplink and the downlink simultaneously andthe uplink data and the downlink data are differentiated via time, it isrequired to insert a guard interval at the downlink-to-uplink switchingpoint, so as to provide a switch guard period and avoid seriousinterference of the downlink communication to the uplink communication.Similarly to the LTE TDD frame structure, a special subframe can beinserted at the downlink-to-uplink switching point, for providing aguard period at the downlink-to-uplink switching point. FIG. 8 shows adata frame structure according to some embodiments of the presentdisclosure. As shown in FIG. 8, the special subframe includes threeparts, respectively are a downlink special slot, a guard period and anuplink pilot slot. The downlink special slot is used for downlinkcommunication, and contents transmitted by this slot can include any oneor any combination of: a downlink data channel, a physicalsynchronization channel, and a physical broadcast channel. The uplinkpilot slot is used for conveying sounding reference signal. The guardperiod does not transmit any signal and is used for providing the timerequired for switching from the downlink to the uplink and avoidinginterference of the downlink transmission to the uplink receiving. Takethe FBMC as an example, considering that its time-domain tail isrelatively long, it is required to provide a relatively long guardperiod to ensure that the downlink data does not generate interfere tothe uplink communication. For example, the FBMC technique with anoverlap factor 4 can require a guard period longer than 4 multicarriersymbols. If a multicarrier modulation technique with a relative shorttime-domain tail is adopted, the guard period can be shorter.

In the in-band hybrid duplex mode provided by the embodiments of thepresent disclosure, the proportion of the uplink and downlink data canbe adjusted according to requirements of downlink and uplink services.For example, it can be adjusted according to the uplink-downlinksubframe proportions as shown in Table 1, wherein the Physical BroadcastChannel (PBCH) is fixedly transmitted in subframe 0, indicating theuplink-downlink configuration used by the radio frame. Therefore, thein-band hybrid duplex mode is able to meet the requirements of variousasymmetric services and has a high flexibility.

Reference signal is required to be inserted in both the data channel andthe control channels, used for demodulation of the data transmitted inrespective channels. In the example as shown in FIG. 7, the referencesignal is transmitted in the first symbol of each resource block. Thechannel state information of other symbols can be obtained via aninterpolation method. Besides the solution as shown in FIG. 7, adiscrete interpolation method of the reference signal similar to the LTEcan also be adopted. At this time, channel estimation of multipletime-frequency points can be obtained through inserting referencesignals in non-consecutive symbols and subcarriers.

In addition, considering that the control channels and the data channelhave different accuracy requirements as to the channel estimation, theinserting frequency of the reference signal in the control channels andthe data channel can also be different. For example, compared with thedata channel, the control channels require a higher accuracy andtherefore have a higher accuracy requirement for the channel estimation.As to the control channels, the inserting frequency of the referencesignal can be increased to some extent, so as to ensure the accuracy ofthe channel estimation of the control channels. At the same time, theinserting frequency of the reference signal in the data channel can bedecreased to some extent to obtain higher spectrum efficiency.

Through the reference signal transmitted in the uplink data subframe andthe uplink pilot slot in the special subframe, the base station is ableto know the channel state information of the uplink channel. Accordingto channel reciprocity, the base station can deduce the downlink channelstate information according to the uplink channel state information andimplement operations such as precoding based on the downlink channelstate information. The reference signal in the downlink data channel isused for estimating an equivalent channel after the precoding, which issimilar to the demodulation reference signal in the LTE. Since channelreciprocity of the uplink and downlink channels can be utilized in thein-band hybrid duplex mode, the downlink physical channel estimation andthe channel state information feedback in the large-scale MIMO techniqueare greatly simplified, which is good for implementations of thelarge-scale MIMO technique and the high frequency band technique in 5G.

In addition, the structure as shown in FIG. 6 is applicable formodulation schemes which do not require adding CP, e.g., FBMC modulationscheme, etc. For modulation schemes which requires CP to reduceInter-symbol interference, e.g., F-OFDM technique, the structure asshown in FIG. 6 needs a slight modification, e.g., after CP is added toeach symbol, the lengths of slot, subframe and radio frame are allchanged, whereas the length of the CP is subject to the utilizedwaveform and factors such as the multipath delay to be restrained. Itshould be noted that, the frame structure, especially whether CP isadded to the multicarrier symbol does not affect the implementation ofthe solution provided by embodiments of the present disclosure. In thesubsequent description, the frame structure as shown in FIG. 6 is stillused as an example. The bandwidth occupied by each channel can beadjusted according to a practical application scenario. For example,considering that the downlink control channel needs to transmit moresignaling compared to the uplink control channel, more bandwidthresources can be allocated to the downlink control channel and thebandwidth allocated to the uplink control channel can be reduced at thesame time.

Embodiment 2

In this embodiment, parameters such as the system frame structure andspectrum structure follow those in embodiment 1. The difference reliesin that, in embodiment 1, the terminal obtains cell-specificuplink-downlink configuration of the data channel via broadcast message.In this embodiment, in order to make the uplink-downlink configurationmore flexible, the uplink-downlink configuration of subframes can beindicated in the downlink control channel. For example, in one possiblemethod, subframe 0 of each radio frame is used for downlinkcommunication; when it is required to switch to uplink communication, anuplink switch indication is transmitted in the downlink control channelof a subframe before the switch; during the uplink communication, if itis required to switch to downlink communication, a downlink switchindication can be transmitted in the downlink control channel in asubframe before the switch. FIG. 9 is a schematic diagram illustratingthe flexible uplink-downlink configuration according to the abovemanner.

In FIG. 9, subframe 0 is used for downlink communication. The basestation inserts an uplink switch indication in the downlink controlchannel of subframe 1, notifying the terminal that the next subframe,i.e., subframe 2 is used for uplink-downlink switch. The structure ofsubframe 2 is similar to the special subframe as shown in FIG. 8,including downlink communication, guard period and uplink communicationthree parts. The guard period is used for providing protection when thedownlink communication is switched to uplink communication. The detailedstructure of subframe 2 can be further indicated in the downlink controlchannel. Subframes 3, 4, 5 and 6 are all used for uplink communication.The base station inserts a downlink switch indication in the downlinkcontrol channel of subframe 6, indicating that the next subframe of thecurrent subframe, i.e., subframe 7 is switched to downlinkcommunication.

Although the uplink-downlink configuration indicating method as shown inFIG. 9 introduces a certain amount of signaling overhead(uplink/downlink switch indication needs to be inserted in the downlinkcontrol channel), compared with the LTE TDD mode, the uplink-downlinkconfiguration is more flexible. The base station is able to flexiblyadjust the uplink-downlink configuration according to uplink anddownlink data communication requirements.

In order to utilize the channel reciprocity of the TDD mode, it isnecessary to ensure that at least one subframe in each radio frame isused for uplink transmission. It can be defined that at least one uplinkswitch indication needs to be transmitted in the downlink controlsignaling and ensure that there is one complete subframe used for uplinkcommunication.

Embodiment 3

This embodiment provides an example of the flexible configuration of theguard bands. Parameters such as the system frame structure and thespectrum structure follow those in embodiment 1. In embodiment 1, theguard bands of the same size are utilized between the data channel andthe control channels, which is relatively simple and suitable for lowpower small cell scenarios. Considering that the downlink communicationtransmission power is generally high in most cases, whereas the uplinkcommunication receiving power is relatively low, the downlinktransmission (including the data channel and the control channel) willgenerate large interference to the uplink receiving. But the uplinktransmission has relatively little interference to the downlinkreceiving. Although it is simple to use the guard bands of the fixedsize between subbands to prevent leakage interference between thesubbands, as to the interference of uplink transmission to downlinkreceiving, too much reservation results in waste, but too littlereservation is not enough for restraining the adjacent band leakageinterference of the downlink transmission to the uplink receiving.Therefore, it is provided in this embodiment that, as to the guard bandsconfigured in advance, the size of the guard bands can be adjustedaccording to the situation of the interference.

FIG. 10 is a schematic diagram illustrating the in-band hybrid duplexmode in which guard bands are inserted in the data channel according tosome embodiments of the present disclosure. As shown in FIG. 10,subframe 0 and a downlink special slot in a subsequent special subframeare used for downlink communication and will generate interference tothe uplink control channel in the adjacent band. Through reserving apart of the data channel which is adjacent to the uplink control channelas the guard band, the guard band between the downlink datacommunication and the uplink control channel is enlarged, which enhancesthe protection to the uplink control channel. For example, during thetransmission of subframe 0 and the downlink special slot of subframe 1,five subcarriers adjacent to the uplink control channel are reserved asthe guard band in the data channel and no data is transmitted on thesesubcarriers. Thus, compared to the structure as shown in FIG. 8, theguard band between the downlink data communication and the uplinkcontrol channel is enlarged to 10 subcarriers, i.e., 3 MHz, which isable to provide a better protection to the uplink control channel.

Similarly, the uplink pilot slot in subframe 1 and the subsequentsubframes 2, 3 and 4 are used for uplink transmission and will beinterfered by the downlink control channel of the adjacent band. Inorder to reduce the interference, some carriers in the uplink pilot slotof subframe 1 and the subframes 2, 3 and 4 adjacent to the downlinkcontrol channel are reserved as the guard band. For example, fivesubcarriers are reserved and no data is transmitted on thesesubcarriers. Thus, the guard band between the downlink control channeland the uplink communication is enlarged to 3 MHz, which can provide abetter protection to the uplink data communication.

Although the above manner of inserting additional guard band in the datachannel can reduce the interference of the downlink communication to theuplink, it also reduces effective data band and thus decreases the datatransmission ratio. FIG. 11 is a schematic diagram illustrating anin-band hybrid duplex mode in which guard bands are inserted in thecontrol channel according to some embodiments of the present disclosure.As shown in FIG. 11, through inserting additional guard bands in thecontrol channel, the guard bands between the downlink communication andthe uplink communication can be enlarged and the protection to theuplink communication is enhanced.

Besides the additional guard band insertion manners as shown in FIGS. 10and 11, a combination of the two manners can be adopted to extend theguard bands, i.e., a part of the additional guard band is inserted inthe data channel, and the other part is inserted in the control channel.

Besides the method of inserting additional guard band in the datachannel or the control channel, it is also possible to move the centerfrequency point of the data channel of some subframes to adjust theguard band. For example, FIG. 12 is a schematic diagram illustrating aguard band adjusting manner through adjusting the center frequency pointof the data channel according to some embodiments of the presentdisclosure. Through moving the center frequency point of the subframesused for downlink communication (subframes 0 and 5) and the downlinkspecial slot used for downlink communication in the special subframe,the guard band can be closer to the downlink control channel. At thistime, the guard band between the subframes used for downlinkcommunication in the data channel and the uplink control channel isenlarged. Therefore, better protection can be provided to the uplinkcontrol channel. At the same time, although the guard band between thesubframes used for downlink communication in the data channel and thedownlink control channel is narrowed, since the interference betweenthem is not serious, the system performance is not seriously affected.Similarly, through moving center frequency point of the subframes(subframes 2, 3, 4, 7, 8, 9) used for uplink communication and theuplink pilot slot in the special subframe towards the uplink controlchannel, the guard band between the downlink control channel and thesubframes used for uplink communication in the data channel is enlarged.Thus, better protection can be provided for the uplink datacommunication.

The adjusting of the guard band through moving the center frequencypoint of the data channel ensures that the data rate is not affected.For example, the subframes used for downlink communication in the datachannel are moved 3 subcarriers towards the downlink control channel. Atthis time, the guard band between the subframes used for downlinkcommunication in the data channel and the uplink control channel isextended to 2.4 MHz, whereas the total guard band is still 3 MHz. Theoverhead brought out by the guard band is not changed, but theprotection to the uplink control channel is enhanced.

The mode of the guard band (the inserted position and the size of theguard band or the offset of the data channel center frequency point) canbe stored in the base station and the terminal in form of a looking-uptable. The base station transmits the guard band mode in subframe 0 viathe broadcast channel or downlink control channel. The terminaldetermines the bandwidth and position of the control channels and thedata channel through receiving the guard band mode via the broadcastchannel or the downlink control channel. It is also possible todetermine a fixed base guard band size and an additional guard band sizethrough a predefined method. The terminal implicitly obtains thebandwidth of the data channel according to the uplink-downlinkconfiguration situation of the data channel and the adjacent bandsituation of the control channel. For example, as to the uplink-downlinkconfiguration shown in FIG. 10, the terminal determines through apredefined rule that the data channel needs to take out 5 subcarriers insubframe 3 adjacent to the subband of the downlink control channel,whereas the base guard band is utilized adjacent to the uplink controlchannel.

Since the guard bands are mainly used for preventing the uplinkreceiving signal from being interfered by the downlink transmissionsignal, the base station can also determine the size of the guard bandsthrough measuring the uplink received signal strength and the downlinkcommunication out-of-band leakage. The uplink received signal strengthis mainly subjected to cell size and the distance between the terminaland the base station. Therefore, during the movement of the terminal,the size of the guard bands can be dynamically adjusted to be suitablefor the variation of the channel. In particular, the base station candetermine the size of the guard bands according to the uplink signalreceiving situation and indicate it to the terminal via the broadcastchannel or the downlink control channel. According to correspondingindication, the terminal obtains the bandwidth of the uplink anddownlink control channels, the bandwidth and the center frequency pointof the data channel.

Embodiment 4

This embodiment provides an example for increasing channel reliabilityin an in-band duplex communication system with separated control anddata. The system frame structure and the spectrum structure are the sameas those in embodiment 1. Transmission of the control channel using theone frequency band is unfavorable for transmission conditions with highfrequency selective fading. In order to increase the transmissionreliability of the control channel, this embodiment transmits controlsignaling in a frequency hopping manner to provide frequency diversitygain for the control channel.

One frequency hopping transmission method of the control signaling is asshown in FIG. 13. It can be seen that, uplink and downlink controlchannel transmissions are switched each two subframes (0.2 ms), and aguard interval is inserted at the downlink-to-uplink switching point.The switch can ensure that the uplink control channel experiencesdifferent frequency bands, so as to provide frequency diversity for thecontrol channel and increase the fading resistance capability of thecontrol channel.

It should be noted that, in the above frequency hopping transmissionmanner of the control signaling, the guard interval at thedownlink-to-uplink switching point can be configured flexibly. Thefrequency hopping manner of the control channels can be defined inadvance, or the base station can indicate the frequency hopping mannerin the broadcast channel or the downlink control channel in subframe 0and the terminal acquires the position of the uplink and downlinkcontrol channels according to this indication.

FIG. 14 shows another manner for providing frequency diversity for thecontrol channels according to some embodiments of the presentdisclosure, i.e., transmitting control signaling in the data channel. InFIG. 14, the control signaling in the data channel is transmitted infirst several multicarrier modulation symbols of each subframe. Besidesthe manner as shown in FIG. 14, the control signaling in the datachannel can also be transmitted on several consecutive subcarriers inthe middle. In addition, the downlink special slot in the specialsubframe can also be used for transmitting the downlink controlsignaling.

The control signaling in the data channel can repeat the control data ofthe control channel in corresponding subframes, or can carry additionalcontrol signaling about the subframe where the control signaling islocated.

The two solutions as shown in FIGS. 13 and 14 can be combined, i.e.,using the frequency hopping of the control channel as well as insertingcontrol signaling in the data channel, so as to provide more reliableprotection for the transmission of the uplink and downlink controlsignaling.

Embodiment 5

This embodiment describes HARQ timing sequence and processing manner inthe in-band hybrid duplex mode provided by the present disclosure. Inthis embodiment, the system frame structure and the spectrum structureare the same as those in embodiment 1.

In the in-band hybrid duplex mode, the uplink and downlink controlchannels always exist. Therefore, the timing sequence confusion and lowefficiency problems in the LTE TDD can be avoided. The downlink HARQtransmission adopts an asynchronous manner similar as the LTE, i.e.,merely the timing sequence for transmitting ACK/NACK signal after theterminal receives a data packet is defined. After receiving the ACK/NACKsignal transmitted by the terminal and determining to retransmit thedata packet, the base station indicate, via an HARQ process number inthe downlink control channel of a corresponding subframe, the currentre-transmitted data packet corresponds to which data packet received bythe terminal. Therefore, it is not required to define the timingsequence that the base station re-transmits data for the terminal, i.e.,the base station can re-transmit data asynchronously. It is defined thatthe terminal feeds back ACK/NACK 0.3 ms after receiving the data packet.FIG. 15 shows one possible timing sequence of the downlink HARQ.

The first line in FIG. 15 is the uplink-downlink configuration utilizedby this embodiment. In this configuration, subframes 0 and 5 in the datachannel are used for downlink transmission, subframes 1 and 6 are usedfor special subframes, and other subframes are used for uplinktransmission. Symbol “P” denotes downlink data transmission, and symbol“A” denotes ACK/NACK feedback of data P. It can be seen from FIG. 15that, the ACK/NACK feedback of the data happens 3 subframes after thedata subframe is received, i.e., 0.3 ms later. The ACK/NACK in thesecond line is taken as an example. The terminal receives downlink dataP1 in subframe 0 and transmits, after processing, corresponding ACK/NACKsignal to the base station in the uplink control channel of subframe 4.After processing, if finding that the data packet requiresretransmission, the base station retransmits this data packet in thesubframe after subframe 5, and indicates this to the terminal throughinserting HARQ process number in the corresponding downlink controlchannel.

The HARQ feedback modes of different uplink-downlink configurations aresimilar, i.e., after data is transmitted in the downlink datacommunication subframe, the terminal transmits the ACK/NACK signal ofthe corresponding data packet in the uplink control channel after acertain period of time (0.3 ms in the example shown in FIG. 15). Whenretransmitting the data packet, the base station gives an indication tothe terminal through inserting HARQ process number in the downlinkcontrol channel of the corresponding subframe.

Compared to the downlink HARQ timing sequence of the LTE TDD mode, thein-band hybrid duplex mode provided by the present disclosure does nothave the situation that the uplink control channel resource isinadequate. Therefore, techniques such as ACK/NACK bundling or ACK/NACKmultiplexing are not required, which makes the downlink HARQ feedbacktimely and not complex.

The uplink HARQ timing sequence adopts a manner similar as the LTE,i.e., after uplink grant or uplink ACK/NACK signaling is transmitted inthe downlink, uplink data packet is transmitted in the data channel ofan available uplink subframe after a defined time period. Afterreceiving the uplink data packet, the base station transmits uplinkgrant or uplink ACK/NACK signal in the downlink control channel of asubframe after a predefined time period. FIG. 16 shows one possibleuplink HARQ timing sequence according to some embodiments of the presentdisclosure. It is defined that the base station feeds back 0.3 ms afterreceiving the data. The terminal searches for available uplink subframesfor uplink transmission 0.3 ms after receiving uplink grant or ACK/NACK.

In FIG. 16, P denotes uplink data packet which is transmitted usinguplink subframes in the data channel. G/H denotes uplink grant orACK/NACK signal. The first line in FIG. 16 is the uplink-downlinkconfiguration utilized by this embodiment. Subframes 0 and 5 are usedfor downlink data communication. Subframes 1 and 6 are specialsubframes, and other subframes are used for uplink data communication.The HARQ timing sequence in the second line is taken as an example. Theterminal transmits uplink data in subframe 2. After receivingprocessing, the base station transmits uplink grant or ACK/NACK signalin the downlink control channel of subframe 6. Since the subframe 0.3 mslater is a downlink subframe, the terminal transmits uplink data insubframe 2 of the second radio frame.

In the HARQ timing sequence as shown in the third line of FIG. 16,although the base station transmits the uplink grant or ACK/NACK signalin the subframe 7 of the first radio frame, the subframe 0.3 ms later isused for downlink data communication, and the first uplink data subframe0.3 ms later, i.e., subframe 2 in the second radio frame has been usedfor HARQ feedback, therefore the terminal transmits uplink data insubframe 3 of the second radio frame.

It can be seen that, compared to the uplink HARQ timing sequence in LTETDD, in the uplink HARQ timing sequence shown in FIG. 16, the basestation is able to transmit uplink grant or ACK/NACK signal in thedownlink control channel without the need of waiting for availabledownlink subframe. In the case that the downlink subframes have a lowproportion, this method is able to shorten the HARQ waiting time. Forexample, in the example as shown in FIG. 16, the Round-Trip Time (RTT)is 1.0 ms, i.e., the length of one radio frame, which is shorter thanthe RTT of the LTE TDD mode with the same uplink-downlink configuration,and meets the 1 ms air interface latency required by 5G.

It should be noted that, the latency (0.3 ms) between the receiving ofthe data and the transmission of the ACK/NACK signal in this embodimentis merely an example. In a practical system, the latency can bedetermined according to a device processing capability and a practicalframe structure.

Embodiment 6

This embodiment describes an access and communication procedure betweenthe terminal and the base station in the in-band hybrid duplex modeprovided by the present disclosure. The procedure includes thefollowing.

The terminal finishes a cell searching procedure through receiving asynchronization channel and a broadcast channel in the center of thesecond subband, and obtains the system configuration information throughreading the physical broadcast channel. The time-frequency position ofthe synchronization channel and the time-frequency position of thebroadcast channel are preconfigured in the frame structure. The systemconfiguration information includes at least one of: system bandwidth,uplink-downlink configuration, guard band configuration, and controlchannel frequency hopping configuration.

The terminal obtains the center frequency points and bandwidths of theuplink and downlink control channels, the center frequency and bandwidthof the data channel, and the uplink-downlink configuration according tothe system configuration information in the physical broadcast channel.

The terminal obtains other system configuration information born by thedownlink subframes of the data channel through the downlink controlchannel, and initiates and implements uplink access according to theother system configuration information.

The terminal communicates with the base station according to theappointed uplink-downlink configuration.

The system frame structure and the spectrum structure in this embodimentare the same as those in embodiment 1. The Primary SynchronizationSignal (PSS), Secondary Synchronization Signal (SSS) and the PhysicalBroadcast Channel (PBCH) are all transmitted in the downlink subframe ofthe data channel and the downlink special slot in the adjacent specialsubframe.

The Physical Random Access Channel (PRACH) is transmitted in the uplinkpilot slot of the special subframe, as shown in FIG. 17. FIG. 17 is aschematic diagram illustrating configurations of synchronization channeland the broadcast channel according to some embodiments of the presentdisclosure. The PSS and the SSS are used for cell search. The PBCHcontains system information including system bandwidth anduplink-downlink configuration. The terminal finishes cell searching andsystem synchronization and obtains a cell ID through searching anddetecting the PSS and the SSS after power on. Thereafter, the terminalreads the PBCH, and obtains system information such as system bandwidth,system frame number and system antenna configuration.

In addition, since the in-band hybrid duplex mode differentiates uplinkand downlink data communications via a TDD manner, the terminal stillneeds to obtain the uplink-downlink configuration. This information canbe provided to the terminal implicitly through the position of thespecial subframe, i.e., the base station merely needs to broadcast theposition of the special subframe in the PBCH, and the terminal is ableto determine the uplink-downlink configuration according to the positionof the special subframe. The position of the special subframe can beprovided to the terminal in form of a looking-up table, i.e., theposition of the special subframe is stored in a looking-up table knownby both the base station and the terminal. The base station merelytransmits the index of the position of the special subframe in the PBCH.

Through this index, the terminal obtains the position of the specialsubframe, and lengths of the downlink special slot, the guard period andthe uplink pilot slot in the special subframe, and obtains theuplink-downlink configuration. For example, as shown in FIG. 17, theterminal determines according to the index of the position of thespecial subframe that the subframes 1 and 6 are special subframes, anddetermines from a corresponding mode that subframes 1 and 5 are used fordownlink data communication and subframes 2, 3, 4, 7, 8, 9 are used foruplink communication.

For the in-band hybrid duplex mode provided by the present disclosure,the mode of the guard bands between the control channels and the datachannel needs to be provided to the terminal, i.e., whether the guardbands of the same bandwidth are adopted for different subframes andwhich mode of the guard band is adopted. Similar to the special subframeposition information, the guard band mode is stored in the base stationand the terminal in form of a looking-up table. The base station merelyneeds to broadcast the index of the guard band mode in the looking-uptable through the PBCH. For example, in FIG. 17, the terminal determinesthat the system uses the guard bands of the same bandwidth according tothe index of the guard band mode, and then deduces that the downlinkcontrol channel and the uplink control channel respectively occupies the15 subcarriers on the two ends of the system bandwidth.

After obtaining the system bandwidth and the guard band bandwidth, theterminal is able to determine the data channel bandwidth and theposition of the control channels. The terminal reads the downlinkcontrol channel and finishes uplink access through reading other systemconfiguration information (such as random access configurationinformation, etc.) in the dynamic broadcast channel in the downlinksubframes of the data channel, then communicates with the base stationaccording to scheduling information of the base station (e.g., flexiblyconfigured uplink-downlink configuration information) or appointeduplink-downlink configuration.

For the situation of the flexible uplink-downlink configuration as shownin embodiment 2, it is required to reserve time-frequency resources forthe uplink physical random access channel. In order to avoid additionalsignaling overhead, before the terminal finishes the access,communication can be implemented according to the uplink-downlinkconfiguration predefined in the PBCH.

In accordance with the above method, the present disclosure alsoprovides a base station. The structure of the base station is shown inFIG. 18. The base station includes a control transmitting module and adata transmitting module. The control transmitting module is adapted torespectively transmit an uplink control channel and a downlink controlchannel in a first subband and a third subband of an available un-pairedspectrum, wherein control channels of reverse directions are transmittedin the first subband the third subband at the same time. The datatransmitting module is adapted to transmit uplink data and downlink dataaccording to a time division multiplexing mode in a second subband ofthe available un-paired spectrum, wherein the first subband and thethird subband are respectively on the two ends of the availableun-paired spectrum.

In accordance with the above method, the present disclosure alsoprovides a terminal. The structure of the terminal is as shown in FIG.19. The terminal includes a cell searching module, a configurationinformation obtaining module, an access module and a communicationmodule. The cell searching module, the configuration informationobtaining module and the access module can be implemented by one or moreprocessors. The cell searching module is adapted to implement a cellsearching procedure through receiving a synchronization channel and abroadcast channel in the center of a second subband, and obtain systemconfiguration information through reading the physical broadcastchannel. The time-frequency position of the synchronization channel andtime-frequency position of the broadcast channel are predefined in aframe structure, and the system configuration information includes atleast one of system bandwidth, uplink-downlink configuration, guard bandconfiguration, and control channel frequency hopping configuration. Theconfiguration information obtaining module is adapted to obtain a centerfrequency points and bandwidths of uplink and downlink control channels,a center frequency point and a bandwidth of a data channel, and anuplink-downlink configuration according to the system configurationinformation in the physical broadcast channel. The access module isadapted to obtain other system configuration information born bydownlink subframes of the data channel according to the downlink controlchannel, and initiate and implement an uplink access according to theother system configuration information; and the communication module isadapted to communicate with the base station according to an appointeduplink-downlink configuration.

Although the present disclosure has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

What is claimed is:
 1. A method for communicating by a base station (BS)with a terminal in a wireless communication system, the methodcomprising: transmitting a downlink control channel in a first subbandof an available un-paired spectrum to the terminal; receiving an uplinkcontrol channel in a third subband of the available un-paired spectrumfrom the terminal, while transmitting the downlink control channel; andtransmitting downlink data on a data channel to the terminal andreceiving uplink data on the data channel from the terminal in a timedivision multiplexing manner in a second subband of the availableun-paired spectrum, wherein the first subband and the third subband areon two ends of the available un-paired spectrum.
 2. The method of claim1, wherein a first guard band exists between the first subband and thesecond subband, a second guard band exists between the second subbandand the third subband, and no signal is transmitted in the first andsecond guard bands.
 3. The method of claim 2, wherein a size of thefirst guard band or the second guard band is determined according to aninterference level of adjacent subbands and an out-of-band leakagesuppression technique being used.
 4. The method of claim 2, furthercomprising: adjusting a size of the guard bands through guard band modeby at least one of: inserting an additional guard band in at least oneof subbands, wherein parameters being adjusted comprise a position and asize of the additional guard band inserted in the control channels orthe data channel; or adjusting a center frequency point of the datachannel in at least one subframe of the second subband, whereinparameters being adjusted comprise an offset of the center frequencypoint of the data channel.
 5. The method of claim 4, further comprising:adjusting a guard band mode dynamically according to uplink receivedsignal strength; and indicating the guard band mode to the terminalthrough a predefined manner or a broadcast channel or the downlinkcontrol channel.
 6. The method of claim 4, further comprising: storing arelationship between a guard band mode and an index of the guard bandmode in a looking-up table; and indicating the guard band mode to theterminal through signaling the index of a currently utilized guard bandmode within the looking-up table.
 7. The method of claim 1, furthercomprising: notifying the terminal of a position and a bandwidth of eachsubband within the available un-paired spectrum, and an uplink-downlinkconfiguration of the data channel; and communicating with the terminalaccording to an appointed transmission configuration.
 8. The method ofclaim 1, wherein the downlink control channel is used for transmittingthe downlink control signaling, wherein the downlink control signalingcomprises at least one of resource allocation information, modulationand coding scheme information, hybrid automatic retransmission requestacknowledgement/negative-acknowledgement information, an uplinktransmission grant, or an uplink transmission power control indication;the uplink control channel is used for receiving the uplink controlsignaling, wherein the uplink control signaling comprises at least oneof scheduling request, hybrid automatic retransmission requestacknowledgement/negative-acknowledgement information, or a channel stateinformation; and the second subband is used for receiving the uplinkdata and transmitting the downlink data, and is further used fortransmitting at least one of a synchronization channel, a broadcastchannel for transmitting system information, or an uplink random accesschannel.
 9. The method of claim 1, further comprising: transmitting atleast one of an uplink switch indication or a downlink switch indicationin the downlink control channel, to change a transmission direction ofsubframes in the data channel.
 10. The method of claim 9, furthercomprising: transmitting at least one uplink switch indication in adownlink control channel of each radio frame, and at least one subframein the data channel is used for uplink data communication.
 11. Themethod of claim 1, further comprising: inserting a guard interval at adownlink-to-uplink switching point in the data channel, wherein nosignal is transmitted during the guard interval.
 12. The method of claim11, further comprising: inserting a special subframe at thedownlink-to-uplink switching point in the data channel; wherein thespecial subframe comprises a downlink special slot, a guard period andan uplink pilot slot, wherein the downlink special slot is used fordownlink communication, and at least one of a downlink data channel, aphysical synchronization channel and a physical broadcast channel istransmitted in the downlink special slot, wherein the uplink pilot slotis used for conveying sounding pilot signal, and wherein no signal istransmitted during the guard period.
 13. The method of claim 1, whereina filtered or filter-bank single carrier or a filtered or filter-bankmulticarrier modulation is adopted for each subband, wherein thefiltered or filter-bank single carrier or filtered or filter-bankmulticarrier modulation comprises any one of filter-bank multicarrier(FBMC), filtered-OFDM, or single-carrier filter-bank multicarrier(SC-FBMC).
 14. A method for communicating by a terminal with a basestation (BS) in a wireless communication system, the method comprising:receiving a downlink control channel in a first subband of an availableun-paired spectrum from the BS; transmitting an uplink control channelin a third subband of the available un-paired spectrum to the BS, whilereceiving the downlink control channel; and receiving downlink data on adata channel from the BS and transmitting uplink data on the datachannel to the BS in a time division multiplexing manner in a secondsubband of the available un-paired spectrum, wherein the first subbandand the third subband are on two ends of the available un-pairedspectrum.
 15. The method of claim 14, further comprising: implementing acell searching procedure through receiving a synchronization channel anda broadcast channel in a center position of a second subband, andobtaining system configuration information through reading the broadcastchannel; obtaining a center frequency point position and a bandwidth ofan uplink control channel and a downlink control channel, a centerfrequency point and a bandwidth of a data channel, and anuplink-downlink configuration, according to the system configurationinformation in the broadcast channel; obtaining other systemconfiguration information born by downlink subframes of a data channelthrough the downlink control channel, and initiating an uplink accessaccording to the other system configuration information; andcommunicating with the BS according to an appointed uplink-downlinkconfiguration, wherein a time-frequency position of the synchronizationchannel and a time-frequency position of the broadcast channel arepreconfigured in a frame structure, and wherein the system configurationinformation comprises at least one of: system bandwidth, uplink-downlinkconfiguration, guard band configuration, and control channel frequencyhopping configuration.
 16. The method of claim 15, further comprising:obtaining the uplink-downlink configuration, the guard bandconfiguration and the control channel frequency hopping configurationthrough receiving an index from the BS respectively, based on predefinedlooking-up table.
 17. The method of claim 15, further comprising:determining a hybrid automatic retransmission requestacknowledgement/negative acknowledgement (HARQ ACK/NACK) positionaccording to a position of subframes used for uplink and downlink datacommunications in the data channel.
 18. A base station (BS)communicating with a terminal in a wireless communication system, the BScomprising: a transceiver is configured to: transmit a downlink controlchannel in a first subband of an available un-paired spectrum to theterminal, receive a uplink control channel in a third subband of theavailable un-paired spectrum from the terminal and transmit downlinkdata on a data channel to the terminal and receive uplink data on thedata channel from the terminal in a time division multiplexing manner ina second subband of the available un-paired spectrum; and a controlleris configured to control the transceiver to transmit the downlinkcontrol channel and receive the uplink control channel at a same time,wherein the first subband and the third subband are on two ends of theavailable un-paired spectrum.
 19. A terminal communicating with a basestation (BS) in a wireless communication system, the terminalcomprising: a transceiver is configured to: receive a downlink controlchannel in a first subband of an available un-paired spectrum from theBS, transmit an uplink control channel in a third subband of theavailable un-paired spectrum to the BS and receive downlink data of adata channel from the BS and transmit uplink data of the data channel tothe BS in a time division multiplexing manner in a second subband of theavailable un-paired spectrum; and a controller is configured to controlthe transceiver to receive the downlink control channel and transmit theuplink control channel at a same time, wherein the first subband and thethird subband are on two ends of the available un-paired spectrum.
 20. Aspectrum structure for communicating between a terminal and a basestation (BS) in a wireless communication system, the spectrum structurecomprising: a first subband is configured to transmit a downlink controlchannel from the BS to the terminal; a second subband is configured totransmit uplink data on a data channel from the terminal to the BS anddownlink data on the data channel from the BS to the terminal in a timedivision multiplexing manner; and a third subband is configured totransmit an uplink control channel from the terminal to the BS, whilethe downlink control channel is being transmitted, wherein the firstsubband and the third subband are on two ends of the spectrum structure,and wherein a first guard band exists between the first subband and thesecond subband, a second guard band exists between the second subbandand the third subband, and no signal is transmitted in the first andsecond guard band.